Input/output panel and semiconductor device having a current sensing circuit

ABSTRACT

A novel input/output panel that is highly convenient and reliable is provided. The input/output panel includes a gate wiring, a first electrode, a second electrode, a current sensing circuit, and a pixel. The first electrode is electrically connected to the gate wiring. The second electrode intersects with the gate wiring and is provided so that capacitance is generated between the first electrode and the second electrode. The current sensing circuit is electrically connected to the second electrode and has a function of sensing a change in the capacitance. The pixel includes a transistor and a display element. The transistor includes a gate electrode, a source electrode, and a drain electrode. The gate electrode is electrically connected to the gate wiring. The display element includes a third electrode and a liquid crystal material. The third electrode is electrically connected to the source electrode or the drain electrode.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to an input/outputpanel, a semiconductor device, and a driving method.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. Furthermore, one embodimentof the present invention relates to a process, a machine, manufacture,or a composition of matter. Specifically, examples of the technicalfield of one embodiment of the present invention disclosed in thisspecification include a semiconductor device, a display device, alight-emitting device, a power storage device, a memory device, a methodfor driving any of them, and a method for manufacturing any of them.

2. Description of the Related Art

A structure in which a common electrode that is for display andoriginally arranged for each liquid crystal display element is used asone electrode (a drive electrode) of a pair of touch sensor electrodes,and the other electrode (a detection electrode for a sensor) is newlyformed, has been known. In addition, a structure in which a commondriving signal existing as a driving signal for display is also used asa driving signal for a touch sensor is known (Patent Document 1).

Touch sensing circuits in which circuit elements, such as touch signallines (e.g., drive lines and sense lines) and grounding regions, indisplay pixel stackups are grouped together, and which sense a touch onor near the display are known (Patent Document 2).

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2009-244958

[Patent Document 2] Japanese Published Patent Application No.2011-197685

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide anovel input/output panel that is highly convenient or reliable. Anotherobject is to provide a novel input/output panel or a novel semiconductordevice.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

(1) An input/output panel of one embodiment of the present inventionincludes a gate wiring, a first electrode, a second electrode, a currentsensing circuit, and a pixel. The first electrode is electricallyconnected to the gate wiring. The second electrode intersects with thegate wiring and is provided so that capacitance is generated between thefirst electrode and the second electrode. The current sensing circuit iselectrically connected to the second electrode and has a function ofsensing a change in the capacitance. The pixel includes a transistor anda display element. The transistor includes a gate electrode, a sourceelectrode, and a drain electrode. The gate electrode is electricallyconnected to the gate wiring. The display element includes a thirdelectrode and a liquid crystal material. The third electrode iselectrically connected to the source electrode or the drain electrode.

(2) In the above embodiment, the third electrode is preferably providedso that an electric field controlling alignment of the liquid crystalmaterial is generated between the second electrode and the thirdelectrode.

(3) In each of the above embodiments, the third electrode preferablyincludes a region positioned between the liquid crystal material and thesecond electrode.

(4) In each of the above embodiments, the display element preferablyincludes a fourth electrode, the third electrode is preferably providedso that an electric field controlling the alignment of the liquidcrystal material is generated between the third electrode and the fourthelectrode, and the fourth electrode is preferably electrically connectedto a wiring supplied with a common potential.

(5) In each of the above embodiments, the third electrode preferablyincludes a region positioned between the liquid crystal material and thefourth electrode.

(6) In each of the above embodiments, the first electrode preferablycontains the same material as the third electrode, and the secondelectrode preferably contains the same material as the fourth electrode.

(7) In each of the above embodiments, a backlight is preferablyprovided, one or both of the second electrode and the third electrodepreferably have reflectance greater than or equal to 5% and less than100% and light transmittance greater than or equal to 1% and less than95% with respect to light with a wavelength in a range greater than orequal to 400 nm and less than 800 nm, and the backlight preferably has afunction of emitting light through the layer containing a liquid crystalmaterial.

(8) In each of the above embodiments, a backlight is preferablyprovided, one or both of the third electrode and the fourth electrodepreferably have reflectance greater than or equal to 5% and less than100% and light transmittance greater than or equal to 1% and less than95% with respect to light with a wavelength in a range greater than orequal to 400 nm and less than 800 nm, and the backlight preferably has afunction of emitting light through the layer containing a liquid crystalmaterial.

(9) An input/output panel of one embodiment of the present inventionincludes a gate wiring, a first electrode, a second electrode, a currentsensing circuit, and a pixel. The first electrode is electricallyconnected to the gate wiring. The second electrode intersects with thegate wiring and is provided so that capacitance is generated between thefirst electrode and the second electrode. The current sensing circuit iselectrically connected to the second electrode and has a function ofsensing a change in the capacitance. The pixel includes a firsttransistor, a second transistor, and a light-emitting element. The firsttransistor includes a first gate electrode, a first source electrode,and a first drain electrode. The second transistor includes a secondgate electrode, a second source electrode, and a second drain electrode.The first gate electrode is electrically connected to the gate wiring.The first source electrode or the first drain electrode is electricallyconnected to the second gate electrode. The second source electrode orthe second drain electrode has a function of supplying electric powerfor driving the light-emitting element.

(10) A semiconductor device of one embodiment of the present inventionincludes one or more of a keyboard, a hardware button, a pointingdevice, a touch sensor, an illuminance sensor, an imaging device, anaudio input device, a sight input device, and a posture determinationdevice, and the above-described input/output panel.

(11) One embodiment of the present invention is a method for driving aninput/output panel including a gate wiring, a signal line, and a pixelelectrically connected to the gate wiring and the signal line. Themethod includes the step of supplying a video signal to the signal lineand sensing proximity of an object to the gate wiring in a period inwhich a selection signal is supplied to the gate wiring.

(12) One embodiment of the present invention is a method for driving aninput/output panel including gate wirings, a signal line, and a pixel.The pixel is electrically connected to the gate wiring and the signalline and includes a display element. The method includes first to thirdperiods. In the first period, predetermined voltage is supplied to thesignal line. In the second period, a selection signal is supplied to thegate wirings in a predetermined order so that all the gate wirings aresupplied with the selection signal, and proximity of an object to thegate wirings is sensed. In the third period, a selection signal issupplied to the gate wirings in a predetermined order so that all thegate wirings are supplied with the selection signal, and a video signalis supplied to the signal line.

(13) One embodiment of the present invention is a method for driving aninput/output panel including gate wirings, a signal line, and a pixel.The pixel is electrically connected to the gate wiring and the signalline and includes a display element. The method includes first to thirdperiods. In the first period, predetermined voltage is supplied to thesignal line. In the second period, a selection signal is supplied togroups of adjacent gate wirings in a predetermined order group by groupso that all the gate wirings are supplied with the selection signal, andproximity of an object to the groups of adjacent gate wirings is sensed.In the third period, a selection signal is supplied to the gate wiringsin a predetermined order so that all the gate wirings are supplied withthe selection signal, and a video signal is supplied to the signal line.

(14) One embodiment of the present invention is a method for driving aninput/output panel including a first display region and a second displayregion. The first display region is adjacent to the second displayregion. The first display region includes a group of gate wirings and asignal line. The second display region includes another group of gatewirings and a signal line. The method includes first to sixth periods.In the first period, predetermined voltage is supplied to the signalline. In the second period, a selection signal is supplied to the groupof gate wirings and proximity of an object to the group of gate wiringsis sensed. In the third period, a selection signal is supplied to thegroup of gate wirings in a predetermined order one by one so that thegroup of gate wirings is supplied with the selection signal, and a videosignal is supplied to the signal line. In the fourth period,predetermined voltage is supplied to the signal line. In the fifthperiod, a selection signal is supplied to the other group of gatewirings and proximity of an object to the other group of gate wirings issensed. In the sixth period, a selection signal is supplied to the othergroup of gate wirings in a predetermined order one by one so that theother group of gate wirings is supplied with the selection signal, and avideo signal is supplied to the signal line.

In this specification, the terms “source” and “drain” of a transistorinterchange with each other depending on the polarity of the transistoror the levels of potentials applied to the terminals. In general, in ann-channel transistor, a terminal to which a lower potential is appliedis called a source, and a terminal to which a higher potential isapplied is called a drain. In a p-channel transistor, a terminal towhich a lower potential is applied is called a drain, and a terminal towhich a higher potential is applied is called a source. In thisspecification, although connection relation of the transistor isdescribed assuming that the source and the drain are fixed forconvenience in some cases, actually, the names of the source and thedrain interchange with each other depending on the relation of thepotentials.

Note that in this specification, a “source” of a transistor means asource region that is part of a semiconductor film or a source electrodeconnected to the semiconductor film. Similarly, a “drain” of atransistor means a drain region that is part of the semiconductor filmor a drain electrode connected to the semiconductor film. A “gate” meansa gate electrode.

Note that in this specification, a state in which transistors areconnected to each other in series means, for example, a state in whichonly one of a source and a drain of a first transistor is connected toonly one of a source and a drain of a second transistor. In addition, astate in which transistors are connected to each other in parallel meansa state in which one of a source and a drain of a first transistor isconnected to one of a source and a drain of a second transistor and theother of the source and the drain of the first transistor is connectedto the other of the source and the drain of the second transistor.

In this specification, the term “connection” means electrical connectionand corresponds to a state where current, voltage, or a potential can besupplied or transmitted. Accordingly, connection means not only directconnection but also indirect connection through a circuit element suchas a wiring, a resistor, a diode, or a transistor so that current, apotential, or voltage can be supplied or transmitted.

In this specification, even when different components are connected toeach other in a circuit diagram, there is actually a case where oneconductive film has functions of a plurality of components such as acase where part of a wiring serves as an electrode. The term“connection” also means such a case where one conductive film hasfunctions of a plurality of components.

Furthermore, in this specification, one of a first electrode and asecond electrode of a transistor refers to a source electrode and theother refers to a drain electrode.

According to one embodiment of the present invention, a novelinput/output panel that is highly convenient or reliable can beprovided. According to another embodiment of the present invention, anovel input/output panel or a novel semiconductor device can beprovided.

Note that the descriptions of these effects do not disturb the existenceof other effects. One embodiment of the present invention does notnecessarily achieve all the effects listed above. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are circuit diagrams each illustrating a structure of aninput/output panel of an embodiment;

FIGS. 2A and 2B are plan views each illustrating a structure of aninput/output panel of an embodiment;

FIGS. 3A and 3B are a cross-sectional view and a plan view illustratinga structure of an input/output panel of an embodiment;

FIGS. 4A and 4B are a cross-sectional view and a plan view illustratinga structure of an input/output panel of an embodiment;

FIGS. 5A and 5B are schematic views illustrating a structure of a mutualcapacitive touch sensor and input and output waveforms of an embodiment,and FIG. 5C illustrates a structure example of a touch sensor of anembodiment that is provided with a plurality of capacitors arranged in amatrix;

FIGS. 6A and 6B are a cross-sectional view and a plan view illustratinga structure of an input/output panel of an embodiment;

FIGS. 7A and 7B are a cross-sectional view and a plan view illustratinga structure of an input/output panel of an embodiment;

FIGS. 8A and 8B are a cross-sectional view and a plan view illustratinga structure of an input/output panel of an embodiment;

FIGS. 9A and 9B are a block diagram of wirings and a timing chart ofinput and output waveforms of an embodiment;

FIG. 10 is a timing chart of input and output waveforms of anembodiment;

FIG. 11 is a timing chart of input and output waveforms of anembodiment;

FIG. 12 is a timing chart of input and output waveforms of anembodiment;

FIG. 13 is a timing chart of input and output waveforms of anembodiment;

FIG. 14 is a block diagram of wirings in a touch panel of an embodiment;

FIGS. 15A and 15B are a cross-sectional view and a plan viewillustrating a structure of an input/output panel of an embodiment;

FIGS. 16A and 16B are a cross-sectional view and a plan viewillustrating a structure of an input/output panel of an embodiment;

FIGS. 17A and 17B are a cross-sectional view and a circuit diagramillustrating a structure of an input/output panel of an embodiment;

FIGS. 18A and 18B are cross-sectional views each illustrating astructure of an input/output panel of an embodiment;

FIGS. 19A to 19E illustrate electronic devices each including aninput/output panel of an embodiment;

FIGS. 20A to 20E illustrate electronic devices each including aninput/output panel of an embodiment;

FIGS. 21A to 21D illustrate structures of transistors that can be usedin an input/output panel of an embodiment;

FIGS. 22A to 22C illustrate a structure of a transistor that can be usedin an input/output panel of an embodiment;

FIG. 23 illustrates an electronic device including an input/output panelof an embodiment;

FIG. 24 is a circuit diagram of a touch sensor of an embodiment;

FIGS. 25A and 25B are a block diagram and a timing chart of a displaydevice of an embodiment;

FIGS. 26A to 26D show operation of a display device and a touch sensorof an embodiment; and

FIGS. 27A to 27D show operation of a display device and a touch sensorof an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescription, and it will be readily appreciated by those skilled in theart that modes and details can be modified in various ways withoutdeparting from the spirit and the scope of the present invention. Thus,the present invention should not be construed as being limited to thedescription in the following embodiments.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Furthermore, the same hatching pattern isapplied to portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

Note that in each drawing described in this specification, the size, thelayer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, the size, the layer thickness, or theregion is not limited to the illustrated scale.

Note that in this specification and the like, ordinal numbers such as“first,” “second,” and the like are used in order to avoid confusionamong components and do not limit the number.

In this specification and the like, a metal oxide means an oxide ofmetal in a broad sense. Metal oxides are classified into an oxideinsulator, an oxide conductor (including a transparent oxide conductor),an oxide semiconductor (also simply referred to as an OS), and the like.For example, a metal oxide used in an active layer of a transistor iscalled an oxide semiconductor in some cases. In other words, a metaloxide that has at least one of an amplifying function, a rectifyingfunction, and a switching function can be called a metal oxidesemiconductor, or OS for short. In addition, an OS FET is a transistorincluding a metal oxide or an oxide semiconductor.

In this specification and the like, a metal oxide including nitrogen isalso called a metal oxide in some cases. Moreover, a metal oxideincluding nitrogen may be called a metal oxynitride.

In this specification and the like, “c-axis aligned crystal (CAAC)” or“cloud-aligned composite (CAC)” might be stated. Note that CAAC refersto an example of a crystal structure, and CAC refers to an example of afunction or a material composition.

In this specification and the like, a CAC-OS or a CAC metal oxide has aconducting function in a part of the material and has an insulatingfunction in another part of the material; as a whole, the CAC-OS or theCAC metal oxide has a function of a semiconductor. In the case where theCAC-OS or the CAC metal oxide is used in an active layer of atransistor, the conducting function is to allow electrons (or holes)serving as carriers to flow, and the insulating function is to not allowelectrons serving as carriers to flow. By the complementary action ofthe conducting function and the insulating function, the CAC-OS or theCAC metal oxide can have a switching function (on/off function). In theCAC-OS or the CAC metal oxide, separation of the functions can maximizeeach function.

In this specification and the like, the CAC-OS or the CAC metal oxideincludes conductive regions and insulating regions. The conductiveregions have the above-described conducting function, and the insulatingregions have the above-described insulating function. In some cases, theconductive regions and the insulating regions in the material areseparated at the nanoparticle level. In some cases, the conductiveregions and the insulating regions are unevenly distributed in thematerial. The conductive regions are observed to be coupled in acloud-like manner with their boundaries blurred, in some cases.

Furthermore, in the CAC-OS or the CAC metal oxide, the conductiveregions and the insulating regions each have a size of more than orequal to 0.5 nm and less than or equal to 10 nm, preferably more than orequal to 0.5 nm and less than or equal to 3 nm and are dispersed in thematerial, in some cases.

The CAC-OS or the CAC metal oxide includes components having differentbandgaps. For example, the CAC-OS or the CAC metal oxide includes acomponent having a wide gap due to the insulating region and a componenthaving a narrow gap due to the conductive region. In the case of such acomposition, carriers mainly flow in the component having a narrow gap.The component having a narrow gap complements the component having awide gap, and carriers also flow in the component having a wide gap inconjunction with the component having a narrow gap. Therefore, in thecase where the above-described CAC-OS or the CAC metal oxide is used ina channel region of a transistor, high current drive capability in theon state of the transistor, that is, high on-state current and highfield-effect mobility, can be obtained.

In other words, the CAC-OS or the CAC metal oxide can be called a matrixcomposite or a metal matrix composite.

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescription, and it will be readily appreciated by those skilled in theart that modes and details can be modified in various ways withoutdeparting from the spirit and the scope of the present invention. Thus,the present invention should not be construed as being limited to thedescription in the following embodiments. Note that in structures of theinvention described below, the same portions or portions having similarfunctions are denoted by the same reference numerals in differentdrawings, and a description of such portions is not repeated.

Embodiment 1

In this embodiment, a structure example of a sensor that can senseproximity or touch of an object (hereinafter, the sensor is alsoreferred to as a touch sensor) and can be used in an input/output panelof one embodiment of the present invention will be described. Theinput/output panel of one embodiment of the present invention includes adisplay element.

A capacitive touch sensor is used as the touch sensor of one embodimentof the present invention. Examples of the capacitive touch sensor aretypically of a surface capacitive type and a projected capacitive type.Examples of the projected capacitive type are of a self capacitive typeand a mutual capacitive type mainly in accordance with the difference inthe driving method. Here, the use of a mutual capacitive type ispreferable because of simultaneous sensing of multiple points (alsoreferred to as multipoint sensing or multi-touch).

The input/output panel of one embodiment of the present inventionincludes a capacitive sensor. The capacitive sensor includes a pair ofelectrodes. Capacitance is generated between the pair of electrodes. Oneof the pair of electrodes is a sensor electrode connected to a gatewiring. The gate wiring has a function of supplying a selection signal.

The other of the pair of electrodes intersects with the gate wiring.

In one embodiment of the present invention, the other of the pair ofelectrodes is separated from an electrode of a display element. Thisstructure is described with reference to FIG. 1A. In another embodimentof the present invention, the other of the pair of electrodes alsoserves as the electrode of the display element. This structure isdescribed with reference to FIG. 1B.

FIGS. 1A and 1B are each a circuit diagram of a pixel portion in theinput/output panel of one embodiment of the present invention. Theinput/output panel of one embodiment of the present invention includesthe display element that includes a layer containing a liquid crystalmaterial. The input/output panel of one embodiment of the presentinvention also includes the pixel portion. The pixel portion includes aliquid crystal element 3513, a capacitor portion 3514, a capacitivesensor portion 3515, a gate electrode 3516, a gate wiring 3517, acontact region 3518, a source wiring 3519, a transistor 3521, and asensor electrode 3529. The pixel portion also includes a commonelectrode 3522 and a pixel electrode 3523. The common electrode 3522 issupplied with a common potential for driving the liquid crystal element3513. The pixel electrode 3523 is electrically connected to thetransistor 3521. The transistor 3521 can supply a signal from the sourcewiring 3519 to the pixel electrode 3523 in response to the selectionsignal. Note that the transistor 3521 is also referred to as a selectiontransistor. The source wiring 3519 is also simply referred to as asignal line.

In the contact region 3518, the sensor electrode 3529 is electricallyconnected to the gate wiring 3517. Furthermore, the gate electrode 3516is electrically connected to the gate wiring 3517. That is, the gatewiring 3517 functions as an auxiliary wiring of the sensor electrode3529 and a wiring that supplies the selection signal for driving thetransistor 3521.

The common electrode 3522 includes a region that is parallel to thesource wiring 3519. Note that in FIGS. 1A and 1B, a direction indicatedby an arrow R is a row direction and a direction indicated by an arrow Cis a column direction.

The liquid crystal element 3513 includes the common electrode 3522 andthe pixel electrode 3523. An electric field in the layer containing aliquid crystal material can be changed using the common electrode 3522and the pixel electrode 3523.

The pixel portion includes the capacitor portion 3514. The capacitorportion 3514 can accumulate electric charge. Accordingly, voltage neededfor display by the liquid crystal element 3513 can be maintained for aperiod from the selection of the gate wiring 3517 to the next selectionof the gate wiring 3517 (this period is also referred to as one frameperiod). Specifically, voltage between the common electrode 3522 and thepixel electrode 3523 can be maintained. One of two electrodes of thecapacitor portion 3514 that is not electrically connected to the pixelelectrode 3523 is supplied with a common potential. Note that thecapacitor portion 3514 is not illustrated in some drawings.

The input/output panel described with reference to the circuit diagramin FIG. 1A includes a sensor electrode 3527. The sensor electrode 3527is separated from the common electrode 3522.

The capacitive sensor portion 3515 includes the sensor electrode 3529and the sensor electrode 3527. The touch sensor of one embodiment of thepresent invention can sense a change in capacitance between the sensorelectrode 3529 and the sensor electrode 3527 when a finger, a styluspen, or the like approaches the touch sensor. The sensor electrode 3527is supplied with a common potential or a floating potential.

The sensor electrode 3527 includes a region that is parallel to thesource wiring 3519. The sensor electrode 3527 may be provided with anauxiliary wiring.

The input/output panel described with reference to the circuit diagramin FIG. 1B is different from that described with reference to thecircuit diagram in FIG. 1A in that the sensor electrode 3527 is notincluded. The capacitive sensor portion 3515 includes the sensorelectrode 3529 and the common electrode 3522. The touch sensor of oneembodiment of the present invention can sense a change in capacitancebetween the sensor electrode 3529 and the common electrode 3522 when afinger, a stylus pen, or the like approaches the touch sensor.

FIG. 2A is a plan view in which structures of wirings and the like areillustrated over the circuit diagram in FIG. 1A. FIG. 2B is a plan viewin which structures of wirings and the like are illustrated over thecircuit diagram in FIG. 1B. Note that for convenience of description,these plan views do not correspond to the actual sizes or shapes in somecases. In addition, for convenience of description, some wirings and thetransistor 3521 are each represented by a symbol. In FIGS. 2A and 2B,the transistor 3521 does not overlap with the common electrode 3522 orthe pixel electrode 3523; however, the transistor 3521 may overlap withthe common electrode 3522 or the pixel electrode 3523. The transistor3521 can be positioned in such a way in other plan views.

The input/output panels in FIGS. 2A and 2B each include the gate wiring3517, the common electrode 3522, the pixel electrode 3523, the sensorelectrode 3529, and the contact region 3518. In each of FIGS. 2A and 2B,the capacitor portion 3514 is not illustrated. The input/output panel inFIG. 2A includes the sensor electrode 3527.

The input/output panels in FIGS. 2A and 2B each include a region wherethe common electrode 3522 is positioned between the gate wiring 3517 andthe sensor electrode 3529.

In the input/output panels in FIGS. 2A and 2B, the pixel electrode 3523and the sensor electrode 3529 contain the same material. Accordingly,the pixel electrode 3523 and the sensor electrode 3529 can be formedthrough the same process. In the input/output panel in FIG. 2A, thecommon electrode 3522 and the sensor electrode 3527 contain the samematerial. Accordingly, the common electrode 3522 and the sensorelectrode 3527 can be formed through the same process.

An auxiliary wiring can be provided for the common electrode 3522. Thiscan reduce wiring resistance and decrease the size of a pixel.

The source wiring 3519 may be provided to overlap with an electrodesupplied with a common potential or a floating potential. Such astructure can reduce an adverse effect of noise due to the sensorelectrode or an object (e.g., a finger). For example, an adverse effecton a video signal, which is supplied from the source wiring 3519, can bereduced.

A method for forming the input/output panel of the present invention isnot limited to the above as long as the circuit in FIG. 1A or FIG. 1B isformed. For example, the gate wiring 3517, the sensor electrode 3529,and the common electrode 3522 may be formed in this order from thesubstrate side. In addition, the pixel electrode 3523 and the sensorelectrode 3529 may be formed of different materials. In addition, thecommon electrode 3522 and the sensor electrode 3527 may be formed ofdifferent materials.

Structure Example 1

The input/output panel described with reference to the circuit diagramin FIG. 1A includes the sensor electrode 3527. The sensor electrode 3527is separated from the common electrode 3522. Part of a structure of apixel in an input/output panel 3551 is described with reference to aschematic cross-sectional view in FIG. 3A, for example. The input/outputpanel 3551 includes a layer 3524 containing a liquid crystal material.The input/output panel 3551 includes a liquid crystal element thatoperates in a fringe field switching (FFS) mode.

The input/output panel 3551 includes the transistor 3521, the commonelectrode 3522, the pixel electrode 3523, the layer 3524 containing aliquid crystal material, and a color filter 3525 (see FIG. 3A). Thepixel electrode 3523 includes a pixel electrode 3523A and a pixelelectrode 3523B. The pixel electrode 3523A and the pixel electrode 3523Bare electrically connected to each other. The layer 3524 containing aliquid crystal material is positioned between an alignment film 3561 andan alignment film 3562. The pixel electrodes 3523A and 3523B areelectrically connected to one of a source electrode and a drainelectrode of the transistor 3521.

The pixel electrodes 3523A and 3523B are parts of the pixel electrode.The pixel electrodes 3523A and 3523B are provided over the commonelectrode 3522 with an insulating layer positioned between the pixelelectrodes and the common electrode. The liquid crystal element includesa pair of electrodes. The pixel electrodes 3523A and 3523B are one ofthe pair of electrodes, and the common electrode 3522 is the other ofthe pair of electrodes. The alignment of the liquid crystal materialcontained in the layer 3524 can be controlled by applying voltagebetween the pair of electrodes of the liquid crystal element.

The gate wiring 3517 contains the same material as the gate electrode3516 of the transistor 3521. Accordingly, the gate wiring 3517 and thegate electrode 3516 can be formed through the same process. In addition,the gate wiring 3517 and the gate electrode 3516 can be electricallyconnected to each other. In addition, the gate wiring 3517 and thesensor electrode 3529 can be electrically connected to each other in thecontact region 3518.

The sensor electrode 3527 contains the same material as the commonelectrode 3522. Accordingly, the sensor electrode 3527 and the commonelectrode 3522 can be formed through the same process.

The input/output panel 3551 in FIG. 3A includes the sensor electrode3529 and the sensor electrode 3527. An electric field generated betweenthe sensor electrode 3529 and the sensor electrode 3527 is indicated bya dashed line 3563. FIG. 3A also illustrates a conductive object 3564across the electric field, for example. Note that the sensor electrode3529 and the sensor electrode 3527 correspond to the pair of electrodesof the capacitive sensor portion 3515 in the input/output paneldescribed with reference to the circuit diagram in FIG. 1A.

The layer 3524 containing a liquid crystal material is positionedbetween a substrate 3543 and a substrate 3541.

FIG. 3B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3551 in FIG. 3A.

In this specification, the line Am-An and the line Bm-Bn in across-sectional view correspond to the line Am-An and the line Bm-Bn ina corresponding plan view, respectively. Note that m and n are each anatural number.

The transistor 3521 can be provided to overlap with the common electrode3522 or the pixel electrode 3523. The gate electrode 3516 of thetransistor 3521 is electrically connected to the gate wiring 3517. Thesource electrode and the drain electrode of the transistor 3521 containthe same material as the source wiring 3519. Accordingly, the sourceelectrode, the drain electrode, and the source wiring 3519 can be formedthrough the same process. In addition, the source electrode or the drainelectrode can be electrically connected to the source wiring 3519. Notethat in other plan views, the transistor can be provided to overlap withthe common electrode or the pixel electrode.

The transistor 3521 may be a bottom-gate transistor, a top-gatetransistor, or a transistor including two gate electrodes, as describedin Embodiment 7.

Part of the electric field generated between the sensor electrode 3529and the sensor electrode 3527 is indicated by the dashed line 3563 (seeFIG. 3B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Notethat the sensor electrode 3529 and the sensor electrode 3527 correspondto the pair of electrodes of the capacitive sensor portion 3515 (seeFIG. 1A).

Structure Example 2

The input/output panel described with reference to the circuit diagramin FIG. 1B includes the common electrode 3522 and the sensor electrode3529. Part of a structure of a pixel in an input/output panel 3552 isdescribed with reference to a schematic cross-sectional view in FIG. 4A,for example. The input/output panel 3552 includes the layer 3524containing a liquid crystal material. The input/output panel 3552includes a liquid crystal element that operates in an FFS mode.

The input/output panel 3552 in FIG. 4A is different from theinput/output panel 3551 in FIG. 3A in that the sensor electrode 3527 isnot included.

The input/output panel 3552 in FIG. 4A includes the sensor electrode3529 and the common electrode 3522. An electric field generated betweenthe sensor electrode 3529 and the common electrode 3522 is indicated bythe dashed line 3563. FIG. 4A also illustrates the conductive object3564 across the electric field, for example. The components other thanthe above are the same as the corresponding components in theinput/output panel 3551 in FIG. 3A. Note that the sensor electrode 3529and the common electrode 3522 correspond to the pair of electrodes ofthe capacitive sensor portion 3515 in the input/output panel describedwith reference to the circuit diagram in FIG. 1B.

FIG. 4B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3552 in FIG. 4A.

Part of the electric field generated between the sensor electrode 3529and the common electrode 3522 is indicated by the dashed line 3563 (seeFIG. 4B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Notethat the sensor electrode 3529 and the common electrode 3522 correspondto the pair of electrodes of the capacitive sensor portion 3515 (seeFIG. 1B).

[Example of Sensing Method of Sensor]

FIGS. 5A and 5B are schematic views illustrating a structure of a mutualcapacitive touch sensor and input and output waveforms. The touch sensorincludes a pair of electrodes. Capacitance is generated between the pairof electrodes. Input voltage is input to one of the pair of electrodes.Furthermore, a current sensing circuit that senses current flowing inthe other of the pair of electrodes (or a potential of the other of thepair of electrodes) is provided.

For example, in the case where a square wave is used as an input voltagewaveform as illustrated in FIG. 5A, a waveform having a sharp peak isdetected as an output current waveform.

Furthermore, in the case where a conductive object is proximate to ortouches a capacitor as illustrated in FIG. 5B, the capacitance valuebetween the electrodes is decreased; accordingly, the value of outputcurrent is decreased.

By sensing a change in capacitance by using a change in output current(or potential) with respect to input voltage in this manner, the touchsensor of one embodiment of the present invention can sense proximity ora touch of an object.

[Structure Example of Touch Sensor]

FIG. 5C illustrates a structure example of a touch sensor provided witha plurality of capacitors arranged in a matrix.

The touch sensor includes a plurality of wirings 3510 extending in an Xdirection (the horizontal direction of this figure) and a plurality ofwirings 3511 extending in a Y direction (the vertical direction of thisfigure) which intersect with the plurality of wirings 3510. A capacitor3503 is formed between two wirings intersecting with each other. Thewiring 3510 corresponds to the gate wiring 3517 and the sensor electrode3529 in the input/output panel 3551, and the wiring 3511 corresponds tothe sensor electrode 3527 in the input/output panel 3551, for example(see FIGS. 3A and 3B).

One of input voltage and a common potential (including a groundpotential and a reference potential) is input to the wirings 3510extending in the X direction. This potential can be supplied from, forexample, a pulse voltage output circuit 3501 that inputs a square wave.Furthermore, a current sensing circuit 3502 (e.g., a source meter or asense amplifier) is electrically connected to the wirings 3511 extendingin the Y direction and can sense current (or potential) flowing throughthe wirings.

The touch sensor can perform sensing of an object two dimensionally insuch a manner that the touch sensor sequentially scans the plurality ofwirings 3510 extending in the X direction so that input voltage is inputand senses a change in current (or potential) flowing through thewirings 3511 extending in the Y direction.

Embodiment 2

This embodiment will describe a structure example of a sensor that canbe used in the input/output panel of one embodiment of the presentinvention and is different from the structure example in Embodiment 1.The input/output panel of one embodiment of the present inventionincludes the display element. The input/output panel described in thisembodiment includes a liquid crystal element including a layercontaining a liquid crystal material and operating in an FFS mode.

Structure Example 3

The input/output panel described with reference to the circuit diagramin FIG. 1B includes the common electrode 3522 and the sensor electrode3529. Part of a structure of a pixel in an input/output panel 3553 isdescribed with reference to a schematic cross-sectional view in FIG. 6A,for example.

The input/output panel 3553 includes the transistor 3521, the commonelectrode, and the pixel electrode 3523 (see FIG. 6A). The commonelectrode includes a common electrode 3522A and a common electrode3522B. The common electrode 3522A and the common electrode 3522B areelectrically connected to each other. The pixel electrode 3523 containsthe same material as the sensor electrode 3529. Accordingly, the pixelelectrode 3523 and the sensor electrode 3529 can be formed through thesame process.

FIG. 6B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3553 in FIG. 6A.

Part of an electric field generated between the sensor electrode 3529and the common electrode 3522A is indicated by the dashed line 3563 (seeFIG. 6B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Anopening is provided in the common electrode 3522B. Accordingly, theelectric field across which the object is likely to pass can begenerated between the sensor electrode 3529 and the common electrode3522A. Note that the sensor electrode 3529 and the common electrode3522A correspond to the pair of electrodes of the capacitive sensorportion 3515 (see FIG. 1B).

For the other components of the input/output panel 3553, the componentsof the input/output panel 3552 can be referred to.

Structure Example 4

The input/output panel described with reference to the circuit diagramin FIG. 1B includes the common electrode 3522 and the sensor electrode3529. Part of a structure of a pixel in an input/output panel 3554 isdescribed with reference to a schematic cross-sectional view in FIG. 7A,for example.

The input/output panel 3554 includes the transistor 3521, the commonelectrode, and the pixel electrode 3523 (see FIG. 7A). The commonelectrode includes the common electrode 3522A and the common electrode3522B. The common electrode 3522A and the common electrode 3522B areelectrically connected to each other. The pixel electrode 3523 containsthe same material as the sensor electrode 3529. Accordingly, the pixelelectrode 3523 and the sensor electrode 3529 can be formed through thesame process.

FIG. 7B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3554 in FIG. 7A.

Part of the electric field generated between the sensor electrode 3529and the common electrode 3522A is indicated by the dashed line 3563 (seeFIG. 7B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Anopening is provided in the common electrode 3522B, and the sensorelectrode 3529 includes a region overlapping with the opening. Note thatthe common electrode 3522A and the sensor electrode 3529 correspond tothe pair of electrodes of the capacitive sensor portion 3515 (see FIG.1B).

For the other components of the input/output panel 3554, the componentsof the input/output panel 3552 can be referred to.

Structure Example 5

The input/output panel described with reference to the circuit diagramin FIG. 1A includes the sensor electrode 3527 and the sensor electrode3529. Part of a structure of a pixel in an input/output panel 3555 isdescribed with reference to a schematic cross-sectional view in FIG. 8A,for example.

The input/output panel 3555 includes the transistor 3521, the commonelectrode, the sensor electrode 3527, and the pixel electrode 3523 (seeFIG. 8A). The common electrode includes the common electrode 3522A andthe common electrode 3522B. The common electrode 3522A and the commonelectrode 3522B are electrically connected to each other. The commonelectrode contains the same material as the sensor electrode 3527.Accordingly, the common electrode and the sensor electrode 3527 can beformed through the same process.

FIG. 8B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3555 in FIG. 8A.

Part of the electric field generated between the sensor electrode 3529and the sensor electrode 3527 is indicated by the dashed line 3563 (seeFIG. 8B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Anopening is provided in the common electrode 3522B. Accordingly, theelectric field across which the object is likely to pass can begenerated between the sensor electrode 3529 and the sensor electrode3527. Note that the sensor electrode 3529 and the sensor electrode 3527correspond to the pair of electrodes of the capacitive sensor portion3515 (see FIG. 1A).

For the other components of the input/output panel 3555, the componentsof the input/output panel 3551 can be referred to.

Embodiment 3

An example of a method for driving the touch panel of one embodiment ofthe present invention is described below.

FIG. 9A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. In FIG. 9A, the touch sensor includes the pulsevoltage output circuit 3501 and the current sensing circuit 3502.Furthermore, n wirings X1 to Xn represent the wirings 3510 to which apulse voltage is applied, and m wirings Y1 to Ym represent the wirings3511 that sense a change in current. FIG. 9A also illustrates aplurality of capacitors 3503 formed in regions where the plurality ofwirings 3510 overlap with the plurality of wirings 3511. Note thatfunctional replacement between the wirings 3510 and 3511 is possible.

The pulse voltage output circuit 3501 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to Xn. By application of apulse voltage to the wirings X1 to Xn, an electric field is generatedbetween the wirings 3510 and 3511 of the capacitor 3503. When theelectric field between the wirings is shielded, for example, a changeoccurs in the capacitor 3503 (mutual capacitance). Proximity or a touchof an object can be sensed by utilizing this change.

The current sensing circuit 3502 is a circuit for sensing changes incurrent flowing through the wirings Y1 to Ym that are caused by thechange in mutual capacitance in the capacitor 3503. No change in currentvalue is sensed in the wirings Y1 to Ym when there is no proximity ortouch of an object, whereas a decrease in current value is sensed whenmutual capacitance is decreased owing to the proximity or touch of anobject. Note that an integrator circuit or the like is used for sensingof current values.

FIG. 9B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 9A. In FIG. 9B,sensing of an object is performed in all the rows and columns in oneframe period. FIG. 9B shows a period 3601 when an object is not sensed(not touched) and a period 3602 when an object is sensed (touched).Sensed current values of the wirings Y1 to Ym are shown as the waveformsof voltage values.

A pulse voltage is sequentially applied to the wirings X1 to Xn, and thewaveforms of the wirings Y1 to Ym change in response to the pulsevoltage. When there is no proximity or touch of an object, the waveformsof the wirings Y1 to Ym change uniformly in response to changes in thevoltages of the wirings X1 to Xn. The current value is decreased at thepoint of proximity or a touch of an object and accordingly the waveformof the voltage value changes.

The wirings 3510 represented by X1 to Xn in the block diagram in FIG. 9Aeach correspond to the gate wiring 3517 of the input/output paneldescribed in any of the other embodiments. Specifically, the wirings3510 each correspond to the gate wiring 3517 of any of the input/outputpanels 3551 to 3555. For the description of coordinates of thecapacitors 3503 and positions of the wirings in FIG. 9A, the wirings3510 represented by X1 to Xn are arranged in X1 to Xn rows, and thewirings 3511 represented by Y1 to Ym are arranged in Y1 to Ym columns.

A timing chart in FIG. 10 shows input waveforms of voltage applied tothe wirings 3510 in the X1 to Xn rows. A signal 3611 is a signal fordriving a display element. A signal 3612 is a signal for driving a touchsensor. In the input/output panel of one embodiment of the presentinvention, the gate wiring 3517 can supply both of the signals 3611 and3612; thus, the signals 3611 and 3612 for a certain row flow in the gatewiring 3517 in the row, for example. That is, the signals 3611 and 3612can be regarded as selection signals input to the gate wiring 3517 inFIG. 1A or FIG. 1B.

The timing chart in FIG. 10 shows an example of a method for driving aninput/output panel (e.g., the input/output panel 3551) in which thecommon electrode 3522 is separated from the sensor electrode 3527. Avertical axis represents a change in the voltage of the gate wiring. Thewirings X1 to Xn in the display element each correspond to the commonelectrode 3522, and those in the touch sensor each correspond to thesensor electrode 3527. In the above structure, sensing of an object bythe touch sensor and writing to the display element are performed at thesame time. In other words, in a period in which a selection signal isinput to the gate wiring, a video signal is input to the source wiringand proximity of an object to the gate wiring is sensed.

In that case, in a display element at certain coordinates, an intervalbetween a period 3621 for writing a video signal to the display elementand the next period 3621 is a display period 3622. As described above, aperiod 3623 for sensing an object by the touch sensor coincides with theperiod 3621. A cycle in and after one period 3621 and before the nextperiod 3621 corresponds to one frame period 3624.

A timing chart in FIG. 11 shows an example of a method for driving aninput/output panel (e.g., the input/output panel 3552) in which thecommon electrode 3522 serves as one electrode of the liquid crystalelement 3513 and the sensor electrode. The wirings X1 to Xn eachcorrespond to the common electrode 3522 in the display element and thetouch sensor. In the above structure, sensing of an object by the touchsensor and writing to the display element are performed in differentperiods.

In that case, in order to prevent crosstalk between the display elementand the touch sensor at certain coordinates, a period 3625 for writing ablack signal begins after the completion of the period 3621 for writinga video signal to the display element in all the rows. That is, aninterval between the period 3621 and the period 3625 is the displayperiod 3622. After the period 3625 is completed in all the rows, all therows sequentially go through the period 3623 for sensing an object bythe touch sensor. In the period 3623 for sensing an object by the touchsensor that is shown in FIG. 11, the touch sensor measures a differencebetween rising waveforms of gate voltage. Note that the waveforms dependon a potential of the pixel electrode 3523. In order to reduce anadverse effect on the sensing, a signal for writing the black signal issupplied to the source wiring 3519 in the period 3623. After the oneframe period 3624 is completed in this manner, writing of a video signalto the display element is resumed.

When the black signal is written before sensing, the influence of thepotential of the pixel electrode 3523 on potentials between the wirings3510 and the wirings 3511 illustrated in FIG. 5C is constant; thisenables more accurate sensing. A predetermined chromaticity signal maybe used instead of the black signal. Alternatively, predeterminedvoltage may be supplied to the pixel electrode 3523 instead of the blacksignal.

The shorter period 3623, i.e., high-speed sensing, can lengthen thedisplay period 3622 without the extension of the one frame period 3624.

A timing chart in FIG. 12 shows another example of a method for drivingan input/output panel in which the common electrode 3522 serves as thesensor electrode and one electrode of the liquid crystal element 3513that drives the liquid crystal element 3513.

Here, the periods 3623 for sensing an object by the touch sensor in agroup of rows adjacent to each other coincide with each other. Signalsin the group of rows adjacent to each other are supplied to the wirings3511 that sense a change in current, which decreases spatial resolutionof sensing. However, the total length of a sensing period 3626 isshortened; accordingly, high-speed sensing can be performed.

The group of rows adjacent to each other can be, for example, Xr to Xsrows in the structure illustrated in the block diagram in FIG. 9A. Notethat r is an integer greater than or equal to 1 and less than or equalto s, and s is an integer greater than or equal to r and less than orequal to n−1. In this case, s is preferably greater than or equal tor+1. After the processing in the Xr to Xs rows, remaining unprocessedrows are processed. For example, a group of rows from the X(s+1) rowthat are adjacent to each other can be processed in a similar way. Inthis manner, processing in X1 to Xn rows is completed. Note that theabove whole processing may include processing in one row. The number ofrows included in each group of rows adjacent to each other may beinvariable or variable. For example, the common electrode 3522 in theinput/output panel 3552 (see FIG. 4B) is connected to the wiring 3511(see FIG. 9A) that senses a change in current. In other words, the Xr toXs rows can be connected to each other.

A timing chart in FIG. 13 shows another example of a method for drivingan input/output panel in which the common electrode 3522 serves as thesensor electrode and one electrode of the liquid crystal element 3513that drives the liquid crystal element 3513.

In this case, a black signal is sequentially written to display elementsin the group of rows adjacent to each other, sensing is performed in thegroup of rows adjacent to each other at a time, and a video signal issequentially written to the display elements in the group of rowsadjacent to each other. The above processing is performed in a period3627, and the same processing is performed in the next group of rowsadjacent to each other. When one frame period is fixed, the drivingmethod shown in the timing chart in FIG. 13 can lengthen the displayperiod 3622 as compared with the driving method shown in the timingchart in FIG. 12.

Note that the structures described in this embodiment can be used inappropriate combination with any of the structures described in theother embodiments.

Embodiment 4

This embodiment will describe the touch panel of one embodiment of thepresent invention in which the number of wirings 3510 is doubled and thenumber of wirings 3511 is reduced by half, with reference to a blockdiagram in FIG. 14.

The number of capacitors 3503 in the block diagram in FIG. 14 is thesame as the number of capacitors 3503 in the block diagram in FIG. 9A.

In FIG. 14, the touch sensor includes a pulse voltage output circuit3501A and a pulse voltage output circuit 3501B. Furthermore, wirings X1Ato XnA and X1B to XnB represent the 2n wirings 3510 to which a pulsevoltage is applied, and wirings Y1 to Ym represent the m/2 wirings 3511that sense a change in current.

For example, a capacitor 3503A connected to the pulse voltage outputcircuit 3501A can be provided adjacent to a capacitor 3503B connected tothe pulse voltage output circuit 3501B.

The availability of such arrangement can increase the pixel layoutflexibility. For example, the resistance of the wirings 3511 can bereduced by the increased line width of the wirings 3511 while the numberof pixels in the C direction is unchanged.

Note that the structures described in this embodiment can be used inappropriate combination with any of the structures described in theother embodiments.

Embodiment 5

This embodiment will describe a structure example of a sensor that canbe used in the input/output panel of one embodiment of the presentinvention and is different from the structure examples in Embodiment 1and Embodiment 2. Specifically, the input/output panel of one embodimentof the present invention includes a liquid crystal element or alight-emitting element.

Structure Example 6

The input/output panel described with reference to the circuit diagramin FIG. 1A includes the sensor electrode 3527. The sensor electrode 3527is separated from the common electrode 3522. Part of a structure of apixel in an input/output panel 3556 is described with reference to aschematic cross-sectional view in FIG. 15A, for example.

The input/output panel 3556 in FIG. 15A includes a liquid crystalelement that operates in an in-plane switching (IPS) mode.

The input/output panel 3556 includes the transistor 3521, the commonelectrode, and the pixel electrode 3523 (see FIGS. 15A and 15B). Thecommon electrode has a comb-like shape and includes the common electrode3522A and the common electrode 3522B. The common electrode, the pixelelectrode 3523, the sensor electrode 3527, and the sensor electrode 3529contain the same material. Accordingly, the common electrode, the pixelelectrode 3523, the sensor electrode 3527, and the sensor electrode 3529can be formed through the same process.

FIG. 15B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3556 in FIG. 15A.

Part of the electric field generated between the sensor electrode 3529and the sensor electrode 3527 is indicated by the dashed line 3563 (seeFIG. 15B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Notethat the sensor electrode 3529 and the sensor electrode 3527 correspondto the pair of electrodes of the capacitive sensor portion 3515 (seeFIG. 1A).

For the other components of the input/output panel 3556, the componentsof the input/output panel 3551 can be referred to.

Structure Example 7

An input/output panel 3557 in FIG. 16A includes a liquid crystal elementthat operates in a vertical alignment (VA) mode.

The common electrode 3522 is provided so as to face the pixel electrode3523 with the layer 3524 containing a liquid crystal material providedtherebetween. A wiring 3526 is provided to overlap with the commonelectrode 3522. For example, the wiring 3526 can be provided toelectrically connect blocks, which are not illustrated in FIG. 16A, toeach other. The layer 3524 containing a liquid crystal material ispositioned between the common electrode 3522 and the pixel electrode3523. The sensor electrode 3529 contains the same material as the pixelelectrode 3523. Accordingly, the sensor electrode 3529 and the pixelelectrode 3523 can be formed through the same process.

FIG. 16B is a plan view schematically illustrating structures of thewirings and the like of the input/output panel 3557 in FIG. 16A.

Part of the electric field generated between the sensor electrode 3529and the sensor electrode 3527 is indicated by the dashed line 3563 (seeFIG. 16B). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Notethat the sensor electrode 3529 and the sensor electrode 3527 correspondto the pair of electrodes of the capacitive sensor portion 3515 (seeFIG. 1A). Part of the wiring 3526 and part of the common electrode 3522overlap with the pixel electrode 3523. In FIG. 16B, the wiring 3526 andthe common electrode 3522 are not illustrated to avoid complexity of thedrawing.

For the other components of the input/output panel 3557, the componentsof the input/output panel 3551 can be referred to.

Note that the liquid crystal element can be operated in a twistednematic (TN) mode using the input/output panel in FIGS. 16A and 16B.

Structure Example 8

The touch panel of one embodiment of the present invention may include alight-emitting element.

FIG. 17A is a schematic cross-sectional view illustrating part of astructure of a pixel in an input/output panel 3558. The input/outputpanel 3558 includes a light-emitting element. The light-emitting elementincludes the pixel electrode 3523, an electrode 3572, and a layer 3573containing a light-emitting material. The layer 3573 containing alight-emitting material is provided between the pixel electrode 3523 andthe electrode 3572.

A conductive material transmitting visible light is used for theelectrode 3572. Thus, light can be extracted from the light-emittingelement. The extracted light can be visually recognized. For example, aconductive material transmitting visible light can be used for a cathodeor an anode. In this embodiment, a conductive material transmittingvisible light is used for the electrode 3572 serving as a cathode (seeFIG. 17A).

A conductive material reflecting visible light can be used for the pixelelectrode 3523. Specifically, the pixel electrode 3523 can have asingle-layer structure or a stacked-layer structure including any ofmetals such as aluminum, titanium, chromium, nickel, copper, yttrium,zirconium, molybdenum, silver, tantalum, and tungsten or an alloycontaining any of these metals as its main component.

A conductive material transmitting visible light can be used for theelectrode 3572. Specifically, a conductive oxide such as indium oxide,indium tin oxide, indium zinc oxide, zinc oxide, or zinc oxide to whichgallium is added can be used for the electrode 3572. A conductive filmtransmitting visible light is described later.

The pixel electrode 3523 contains the same material as the sensorelectrode 3529. Accordingly, the pixel electrode 3523 and the sensorelectrode 3529 can be formed through the same process. The pixelelectrode 3523 is not connected to the sensor electrode 3529. Theelectrode 3572 includes a region not overlapping with the sensorelectrode 3529. For example, the electrode 3572 includes an openingformed using a shadow mask.

The input/output panel 3558 includes an insulating layer 3576 and aresin layer 3577. The insulating layer 3576 prevents diffusion of waterfrom the resin layer 3577 to the layer 3573 containing a light-emittingmaterial.

The input/output panel 3558 includes the pixel electrode 3523. The pixelelectrode 3523 is electrically connected to one of a source electrodeand a drain electrode of a transistor 3530. The other of the sourceelectrode and the drain electrode of the transistor 3530 is electricallyconnected to a power supply line 3531 (see FIG. 17B). The transistor3530 has a function of controlling the light-emitting element. Thetransistor 3530 is a driving transistor. A gate electrode of thetransistor 3530 is electrically connected to one of the source electrodeand the drain electrode of the switching transistor 3521. The gateelectrode of the switching transistor 3521 is electrically connected tothe gate wiring 3517. The pixel electrode 3523 and the sensor electrode3529 serve as a pair of electrodes, and a change in capacitance issensed, so that capacitive sensing is performed.

A partition 3578, which is used for separate formation of the layer 3573containing a light-emitting material in each pixel, is between the pixelelectrode 3523 and the layer 3573 containing a light-emitting material.The partition 3578 is formed using an inorganic insulating film or anorganic insulating film. As the inorganic insulating film, a siliconnitride film or a silicon nitride oxide film formed by a CVD method oran SOG method can be used, for example. As the organic insulating film,an acrylic resin film or the like can be used.

With the use of a wet etching method, the partition 3578 can be easilyformed to have a tapered sidewall. The sidewall of the partition 3578should have a sufficiently gentle slope; otherwise, the step will causethe serious deterioration of an EL layer.

The partition 3578 is formed also in the contact region 3518. An unevensurface of the pixel electrode due to an uneven surface of the contactregion 3518 is thus filled with the partition 3578, so thatdeterioration of the EL layer caused by the step can be prevented.

Part of the electric field generated between the sensor electrode 3529and the sensor electrode 3527 is indicated by the dashed line 3563 (seeFIG. 17A). The touch sensor of one embodiment of the present inventioncan sense the object 3564 that passes across the electric field. Notethat the sensor electrode 3529 and the sensor electrode 3527 correspondto the pair of electrodes of the capacitive sensor portion 3515 (seeFIG. 1A). Note that any of the driving methods described in FIG. 11,FIG. 12, and FIG. 13 can be used to drive the input/output panel.

The sensor electrode 3527 contains the same material as the electrode3572. Accordingly, the sensor electrode 3527 and the electrode 3572 canbe formed through the same process. The sensor electrode 3527 can beformed apart from the electrode 3572. When the sensor electrode 3527 isused as a common electrode, the sensor electrode 3527 and the sensorelectrode 3529 can be a pair of electrodes of a capacitor portion.

Structure Example 9

An input/output panel 3559 in FIG. 18A is different from theinput/output panel 3551 in FIG. 3A in that the sensor electrode 3527 isformed over the substrate 3543. In this case, the substrate 3543 ispositioned between the sensor electrode 3527 and the layer 3524containing a liquid crystal material.

Formation of the sensor electrode 3527 in the above position enables aline of electric force across which the object 3564 is likely to pass tobe generated between the sensor electrode 3529 and the sensor electrode3527. As a result, the sensitivity of a capacitive sensor can beimproved.

Structure Example 10

A conductive film transmitting visible light can be used for the commonelectrode 3522 of the input/output panel 3557 in FIG. 16A or theelectrode 3572 of the input/output panel 3558 in FIG. 17A. For example,a conductive film whose reflectance is greater than or equal to 1%,preferably greater than or equal to 5% and less than 100% and whoselight transmittance is greater than or equal to 1%, preferably greaterthan or equal to 10% and less than 100% with respect to light with awavelength in a range greater than or equal to 400 nm and less than 800nm can be used for the common electrode 3522 or the electrode 3572.

Specifically, a conductive material containing silver (Ag) or aluminum(Al) and having a thickness of 1 nm to 30 nm, preferably 1 nm to 15 nmcan be used for the common electrode 3522 or the electrode 3572.

A material containing an element selected from indium, tin, zinc,gallium, and silicon can be used for the common electrode 3522 or theelectrode 3572. Specifically, an In oxide, a Zn oxide, an In—Sn oxide(also referred to as ITO), an In—Sn—Si oxide (also referred to as ITSO),an In—Zn oxide, an In—Ga—Zn oxide, or the like can be used for thecommon electrode 3522 or the electrode 3572.

A film containing graphene or graphite can be used for the commonelectrode 3522 or the electrode 3572. Specifically, a film containinggraphene formed by reducing a film containing graphene oxide can beused. Note that the reduction can be performed by applying heat or usinga reducing agent, for example.

A metal oxide typified by an In—Ga—Zn oxide can be used for the commonelectrode 3522 or the electrode 3572. For example, a stacked film inwhich a nitride insulating film such as a silicon nitride film is formedover the metal oxide can be used for the common electrode 3522 or theelectrode 3572. Note that nitrogen or hydrogen can be supplied from thenitride insulating film to the metal oxide by thermal diffusion. Thus, acarrier density of the metal oxide can be increased. Furthermore, themetal oxide can be an oxide conductor (OC).

An oxide conductor having a thickness of greater than or equal to 30 nmand less than or equal to 500 nm, or greater than or equal to 100 nm andless than or equal to 400 nm can be used for the common electrode 3522or the electrode 3572.

A conductive film transmitting visible light can be used for one or moreof the pixel electrode 3523, the sensor electrode 3527, the sensorelectrode 3529, and the electrode 3572. Furthermore, a display region ofa display element can be formed to overlap with any of the electrodesformed using the conductive film transmitting visible light. Thus,display light of the display element can pass through one or more of thepixel electrode 3523, the sensor electrode 3527, the sensor electrode3529, and the electrode 3572. A user can see display that has passedthrough one or more of the pixel electrode 3523, the sensor electrode3527, the sensor electrode 3529, and the electrode 3572.

Structure Example 11

An input/output panel 3560 in FIG. 18B includes a transmissive ortransflective liquid crystal element. The input/output panel 3560 isdifferent from the input/output panel 3551 described with reference toFIG. 3A in Embodiment 1 in that a backlight BL is included. The commonelectrode 3522, the pixel electrode 3523A, and the pixel electrode 3523Btransmit visible light.

The backlight BL emits light L in the direction indicated by an arrow3581. By the backlight BL, the layer 3524 containing a liquid crystalmaterial can be irradiated with light. A direct-below light source or aside light source can be used as the backlight BL, for example.

The input/output panel 3560 includes a functional film 3582. Forexample, a polarizing plate can be used for the functional film 3582.Although not illustrated, another functional film can be provided sothat the layer containing a liquid crystal material is positionedbetween the functional film and the functional film 3582.

A transmissive liquid crystal element including a conductive film havinga function of transmitting visible light can be used in the input/outputpanel described in this specification. A backlight that suppliesdifferent colored light in rotation with a field-sequential color systemenables color display without a coloring film over the liquid crystalelement. When the backlight supplies light of all colors, white displaycan be obtained.

For example, a reflective liquid crystal element and a polarizing platecan be used in the input/output panel 3560. Specifically, the polarizingplate can be provided on the display surface side of the reflectiveliquid crystal element.

A light diffusion plate can be provided on the display surface side ofany of the input/output panels. Accordingly, visibility can be improved.

Note that two or more of the structures of the input/output panelsselected from those in Embodiments 1 to 5 can be used in appropriatecombination. For example, three electrodes can be used in a liquidcrystal element that operates in a mode other than an FFS mode or a VAmode. Alternatively, a display element driven by another display methodcan be used.

This embodiment can be implemented in combination with any of the otherembodiments described in this specification as appropriate.

Embodiment 6

In this embodiment, an example of a method for driving the touch panelof one embodiment of the present invention is described with referenceto drawings.

[Example of Sensing Method of Sensor]

Although FIG. 9A is a passive matrix touch sensor in which only thecapacitor is provided at the intersection of wirings as a touch sensor,an active matrix touch sensor including a transistor and a capacitor maybe used. FIG. 24 is a sensor circuit included in an active matrix touchsensor.

The sensor circuit includes a capacitor 1503 and transistors 1511, 1512,and 1513. A signal G2 is input to a gate of the transistor 1513. Avoltage VRES is applied to one of a source and a drain of the transistor1513, and one electrode of the capacitor 1503 and a gate of thetransistor 1511 are electrically connected to the other of the sourceand the drain of the transistor 1513. One of a source and a drain of thetransistor 1511 is electrically connected to one of a source and a drainof the transistor 1512, and a voltage VSS is applied to the other of thesource and the drain of the transistor 1511. A signal G1 is input to agate of the transistor 1512, and a signal line ML is electricallyconnected to the other of the source and the drain of the transistor1512. The voltage VSS is applied to the other electrode of the capacitor1503.

Next, the operation of the sensor circuit will be described. First, apotential for turning on the transistor 1513 is supplied as the signalG2, and a potential with respect to the voltage VRES is thus applied toa node n connected to the gate of the transistor 1511. Then, a potentialfor turning off the transistor 1513 is applied as the signal G2, wherebythe potential of the node n is held.

Then, mutual capacitance of the capacitor 1503 changes owing to theapproach or contact of an object such as a finger, and accordingly thepotential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 1512 issupplied as the signal G1. Current flowing through the transistor 1511,that is, current flowing through the signal line ML is changed inresponse to the potential of the node n. By sensing this current, theapproach or contact of an object can be sensed.

It is preferable that the transistors 1511, 1512, and 1513 each includean oxide semiconductor in a semiconductor layer where a channel isformed. In particular, by using an oxide semiconductor in asemiconductor layer where a channel of the transistor 1513 is formed,the potential of the node n can be held for a long time and thefrequency of operation (refresh operation) of resupplying VRES to thenode n can be reduced.

[Example of Driving Method for Display Device]

FIG. 25A is a block diagram illustrating an example of a structure of adisplay device. FIG. 25A illustrates a gate driver circuit GD, a sourcedriver circuit SD, and a pixel pix. In FIG. 25A, gate lines x_1 to x_m(m is a natural number) electrically connected to the gate drivercircuit GD and source lines y_1 to y_n (n is a natural number)electrically connected to the source driver circuit SD are illustrated.Corresponding to these lines, the pixels pix are denoted by (1, 1) to(n, m).

FIG. 25B is a timing chart of signals supplied to the gate lines and thesource lines in the display device illustrated in FIG. 25A. The periodsin FIG. 25B show the case where data signals are rewritten every frameperiod and the case where data signals are not rewritten. Note thatperiods such as a retrace period are not taken into consideration inFIG. 25B.

In the case where data signals are rewritten every frame period, scansignals are sequentially supplied to the gate lines x_1 to x_m. In ahorizontal scanning period 1H, during which the scan signal is at an Hlevel, data signals D are supplied to the source lines y_1 to y_n in thecolumns.

In the case where data signals are not rewritten every frame period, thesupply of scan signals to the gate lines x_1 to x_m is stopped. In thehorizontal scanning period 1H, the supply of data signals to the sourcelines y_1 to y_n in the columns is stopped.

A driving method in which data signals are not rewritten every frameperiod is effective particularly when an oxide semiconductor is used fora semiconductor layer where a channel of a transistor included in apixel is formed. A transistor including an oxide semiconductor can havemuch lower off-state current than a transistor including a semiconductorsuch as silicon. Thus, a data signal written in the previous period canbe held without rewriting data signals every frame period, and graylevels of pixels can be held for 1 second or longer, preferably 5seconds or longer, for example.

In the case where polycrystalline silicon is used for a semiconductorlayer where a channel of a transistor included in a pixel is formed, thecapacitance of the pixel is preferably increased in advance. The largerthe capacitance is, the longer the gray level of the pixel can be held.The capacitance may be determined depending on leakage current of atransistor or a display element which is electrically connected to thecapacitance. For example, the capacitance per pixel is set to 5 fF to 5pF inclusive, preferably 10 fF to 5 pF inclusive, further preferably 20fF to 1 pF inclusive, so that a data signal written in the previousperiod can be held without rewriting data signals every frame period.For example, a gray level of a pixel can be held for several frameperiods or several tens of frame periods.

[Examples of Driving Methods for Display Device and Touch Sensor]

FIGS. 26A to 26D show examples of the operations in successive frameperiods of the touch sensor described with reference to FIGS. 9A and 9Band the display device described with reference to FIGS. 25A and 25Bthat are driven for 1 sec (one second). In FIG. 26A, one frame periodfor the display device is 16.7 ms (frame frequency: 60 Hz), and oneframe period for the touch sensor is 16.7 ms (frame frequency: 60 Hz).

In the touch panel of this embodiment, the display device and the touchsensor operate independently of each other, and the touch sensor canhave a touch sensing period concurrent with a display period. Thus, oneframe period for the display device and one frame period for the touchsensor can both be 16.7 ms (frame frequency: 60 Hz) as shown in FIG.26A. The frame frequency for the touch sensor may differ from that forthe display device. For example, as shown in FIG. 26B, one frame periodfor the display device may be 8.3 ms (frame frequency: 120 Hz) and oneframe period for the touch sensor may be 16.7 ms (frame frequency: 60Hz). Although not shown, one frame period for the display device may be33.3 ms (frame frequency: 30 Hz).

The frame frequency for the display device may be changeable, i.e., theframe frequency in displaying moving images may be increased (e.g., 60Hz or more, or 120 Hz or more), whereas the frame frequency indisplaying still images may be decreased (e.g., 60 Hz or less, 30 Hz orless, or 1 Hz or less). With this structure, power consumption of thedisplay device can be reduced. The frame frequency for the touch sensormay be changeable so that the frame frequency in waiting differs fromthe frame frequency in sensing a touch.

The touch panel of this embodiment holds data signals rewritten in theprevious period without rewriting data signals in the display device,and one frame period for the display device can thus be longer than 16.7ms. Thus, as shown in FIG. 26C, one frame period for the display devicecan be 1 sec (frame frequency: 1 Hz) and one frame period for the touchsensor can be 16.7 ms (frame frequency: 60 Hz).

Furthermore, the touch panel of this embodiment can continue to operatethe touch sensor in the driving shown in FIG. 26C. Thus, data signals inthe display device can be rewritten at the timing at which the approachor contact of an object is sensed by the touch sensor, as shown in FIG.26D.

If rewriting of data signals in a display device is performed during asensing period of a touch sensor, noise caused by operating the displaydevice travels through the touch sensor and the sensitivity of the touchsensor might decrease. For this reason, rewriting of data signals in adisplay device and sensing in a touch sensor are preferably performed indifferent periods.

FIG. 27A shows an example in which rewriting of data signals in adisplay device and sensing in a touch sensor are performed alternately.FIG. 27B shows an example in which sensing in a touch sensor isperformed one time every two rewritings of data signals in a displaydevice. Note that sensing in a touch sensor may be performed once everythree or more rewritings.

With the use of an oxide semiconductor for a semiconductor layer where achannel of a transistor used in a pixel of a display device is formed,off-state current can be significantly reduced and the frequency ofrewriting data signals can be sufficiently reduced. Specifically, asufficiently long break period can be set between rewritings of datasignals. The break period is 0.5 seconds or longer, 1 second or longer,or 5 seconds or longer, for example. The upper limit of the break perioddepends on leakage current of a capacitor or a display element connectedto a transistor; for example, 1 minute or shorter, 10 minutes orshorter, 1 hour or shorter, or 1 day or shorter.

FIG. 27C shows an example in which rewriting of data signals in adisplay device is performed once every 5 seconds. A break period forstopping the operation of a display device is set in FIG. 27C betweenrewriting of data signals and next rewriting. In the break period, atouch sensor can be operated at a frame frequency of i Hz (i is morethan or equal to the frame frequency of a display device; here, 0.2 Hzor more). It is preferable that sensing in a touch sensor be performedin a break period and not be performed in a rewriting period of datasignals in a display device as shown in FIG. 27C, in which casesensitivity of a touch sensor can be increased. When rewriting of datasignals in a display device and sensing in a touch sensor are performedat the same time as shown in FIG. 27D, operation signals can besimplified.

In a break period during which rewriting of data signals in a displaydevice is not performed, only the supply of signals to a driver circuitmay be stopped, and in addition, the supply of a power supply potentialmay be stopped in order to further reduce the power consumption.

The touch panel of one embodiment of the present invention includes adisplay device and a touch sensor between two flexible substrates. Withthis structure, the distance between the display device and the touchsensor can be reduced. A decrease in the sensitivity of the touch sensorcaused by noise generated by driving the display device can besuppressed when the driving method in this embodiment is employed, andboth a reduction in thickness and high sensitivity of a touch panel areachieved.

Embodiment 7

In this embodiment, a structure of a transistor typified by thetransistor 3521 in the input/output panel of one embodiment of thepresent invention will be described.

The transistor 3521 may be a bottom-gate transistor, a top-gatetransistor, or a transistor including two gate electrodes.

FIG. 21A illustrates a bottom-gate transistor 151. The transistor 151includes a conductive film 106 over a substrate 102, an insulating film104 over the conductive film 106, a metal oxide film 108 over theinsulating film 104, conductive films 120 a and 120 b over the metaloxide film 108, an insulating film 118 over the metal oxide film 108 andthe conductive films 120 a and 120 b, and an insulating film 122 overthe insulating film 118.

Furthermore, in the transistor 151, the conductive film 106 functions asa gate electrode, the conductive film 120 a functions as a sourceelectrode, and the conductive film 120 b functions as a drain electrode.

In the case where a conductive film 114 is formed over the insulatingfilm 122 and electrically connected to the conductive film 106 servingas the gate electrode of the transistor 151, the conductive film 114 canbe connected to the conductive film 106 in an opening in the insulatingfilms 104, 118, and 122 as illustrated in FIG. 21B.

FIG. 21C illustrates a top-gate transistor 152. The transistor 152includes the insulating film 104 over the substrate 102, the metal oxidefilm 108 over the insulating film 104, an insulating film 110 over themetal oxide film 108, a conductive film 112 over the insulating film110, and an insulating film 116 over the insulating film 104, the metaloxide film 108, and the conductive film 112. The insulating film 118 isover the insulating film 116.

The metal oxide film 108 includes regions 108 n which do not overlapwith the conductive film 112 and are in contact with the insulating film116. The regions 108 n are n-type regions in the metal oxide film 108described above. Note that the regions 108 n are in contact with theinsulating film 116 containing nitrogen or hydrogen. Nitrogen orhydrogen in the insulating film 116 is added to the regions 108 n toincrease the carrier density, thereby making the regions 108 n n-type.

The transistor 152 includes the insulating film 118 over the insulatingfilm 116, the conductive film 120 a electrically connected to the region108 n through an opening 141 a formed in the insulating films 116 and118, and the conductive film 120 b electrically connected to the region108 n through an opening 141 b formed in the insulating films 116 and118.

In the transistor 152, the conductive film 112 functions as a gateelectrode, the conductive film 120 a functions as a source electrode,and the conductive film 120 b functions as a drain electrode.

In the case where the conductive film 114 is formed over the insulatingfilm 122 and electrically connected to the conductive film 112 servingas the gate electrode of the transistor 152, the conductive film 114 canbe connected to the conductive film 112 in an opening in the insulatingfilms 116, 118, and 122 as illustrated in FIG. 21D.

The conductive film 106 of the transistor 151 and the conductive film112 of the transistor 152 can be used as the gate electrode 3516 of thetransistor 3521 in FIGS. 1A and 1B.

The transistor including one gate electrode is described above, and atransistor 150 including two gate electrodes will be described below.The transistor 150 has a structure in which the structure of thetransistor 151 and the structure of the transistor 152 are combined.

FIG. 22A is a top view of the transistor 150. FIG. 22B is across-sectional view taken along the dashed-dotted line X1-X2 in FIG.22A. FIG. 22C is a cross-sectional view taken along the dashed-dottedline Y1-Y2 in FIG. 22A.

The transistor 150 illustrated in FIGS. 22A to 22C includes theconductive film 106 over the substrate 102; the insulating film 104 overthe conductive film 106; the metal oxide film 108 over the insulatingfilm 104; the insulating film 110 over the metal oxide film 108; theconductive film 112 over the insulating film 110; and the insulatingfilm 116 over the insulating film 104, the metal oxide film 108, and theconductive film 112.

The metal oxide film 108 has a structure similar to that described inthe other embodiments. The transistor 150 illustrated in FIGS. 22A to22C includes the conductive film 106 and an opening 143.

The opening 143 is formed in the insulating films 104 and 110. Theconductive film 106 is electrically connected to the conductive film 112through the opening 143. Thus, the same potential is applied to theconductive film 106 and the conductive film 112. Note that differentpotentials may be applied to the conductive film 106 and the conductivefilm 112 without the formation of the opening 143. Alternatively, theconductive film 106 may be used as a light-blocking film without theformation of the opening 143. When the conductive film 106 is formedusing a light-blocking material, for example, light from the bottom thatirradiates the metal oxide film 108 can be reduced.

In the case of the structure of the transistor 150, the conductive film106 functions as a first gate electrode (also referred to as a bottomgate electrode), and the conductive film 112 functions as a second gateelectrode (also referred to as a top gate electrode). The insulatingfilm 104 functions as a first gate insulating film, and the insulatingfilm 110 functions as a second gate insulating film.

The conductive film 106 can be formed using a material similar to thematerials of the conductive films 112, 120 a, and 120 b described above.It is particularly suitable to use a material containing copper for theconductive film 106 because the resistance can be reduced. It issuitable that, for example, each of the conductive films 106, 120 a, and120 b has a stacked-layer structure in which a copper film is over atitanium nitride film, a tantalum nitride film, or a tungsten film. Inthat case, by using the transistor 150 as a pixel transistor and/or adriving transistor of a display device, parasitic capacitance generatedbetween the conductive films 106 and 120 a and between the conductivefilms 106 and 120 b can be reduced. Thus, the conductive films 106, 120a, and 120 b can be used not only as the first gate electrode, thesource electrode, and the drain electrode of the transistor 150, butalso as power source supply wirings, signal supply wirings, connectionwirings, or the like of the display device.

In this manner, the transistor 150 in FIGS. 22A to 22C has a structurein which a conductive film functioning as a gate electrode is providedover and under the metal oxide film 108. As in the transistor 150, asemiconductor device of one embodiment of the present invention may havea plurality of gate electrodes.

In the case where the conductive film 114 is formed over the insulatingfilm 122 and electrically connected to the conductive film 112 or 106serving as the gate electrode of the transistor 150, the conductive film114 can be connected to the conductive film 112 or 106 in an opening inthe insulating films as illustrated in FIG. 21C or FIG. 21D.

As illustrated in FIGS. 22B and 22C, the metal oxide film 108 faces theconductive film 106 functioning as the first gate electrode and theconductive film 112 functioning as the second gate electrode and ispositioned between the two conductive films functioning as the gateelectrodes.

Furthermore, the length of the conductive film 112 in the channel widthdirection is larger than the length of the metal oxide film 108 in thechannel width direction. In the channel width direction, the whole metaloxide film 108 is covered with the conductive film 112 with theinsulating film 110 placed therebetween. Since the conductive film 112is connected to the conductive film 106 through the opening 143 formedin the insulating films 104 and 110, a side surface of the metal oxidefilm 108 in the channel width direction faces the conductive film 112with the insulating film 110 placed therebetween.

In other words, the conductive film 106 and the conductive film 112 areconnected to each other through the opening 143 formed in the insulatingfilms 104 and 110, and each include a region positioned outside an edgeportion of the metal oxide film 108.

Such a structure enables the metal oxide film 108 included in thetransistor 150 to be electrically surrounded by electric fields of theconductive film 106 functioning as the first gate electrode and theconductive film 112 functioning as the second gate electrode. A devicestructure of a transistor, like that of the transistor 150, in whichelectric fields of a first gate electrode and a second gate electrodeelectrically surround the metal oxide film 108 in which a channel regionis formed can be referred to as a surrounded channel (S-channel)structure.

Since the transistor 150 has the S-channel structure, an electric fieldfor inducing a channel can be effectively applied to the metal oxidefilm 108 by the conductive film 106 or the conductive film 112; thus,the current drive capability of the transistor 150 can be improved andhigh on-state current characteristics can be obtained. Since theon-state current can be increased, it is possible to reduce the size ofthe transistor 150. Furthermore, since the transistor 150 has astructure in which the metal oxide film 108 is surrounded by theconductive film 106 and the conductive film 112, the mechanical strengthof the transistor 150 can be increased.

When seen in the channel width direction of the transistor 150, anopening different from the opening 143 may be formed on the side of themetal oxide film 108 on which the opening 143 is not formed.

When a transistor has a pair of gate electrodes between which asemiconductor film is positioned as in the transistor 150, one of thegate electrodes may be supplied with a signal A, and the other gateelectrode may be supplied with a fixed potential V_(b). Alternatively,one of the gate electrodes may be supplied with the signal A, and theother gate electrode may be supplied with a signal B. Alternatively, oneof the gate electrodes may be supplied with a fixed potential V_(a), andthe other gate electrode may be supplied with the fixed potential V_(b).

The signal A is, for example, a signal for controlling the on/off state.The signal A may be a digital signal with two kinds of potentials, apotential V₁ and a potential V₂ (V₁>V₂). For example, the potential V₁can be a high power supply potential, and the potential V₂ can be a lowpower supply potential. The signal A may be an analog signal.

The fixed potential V_(b) is, for example, a potential for controlling athreshold voltage V_(thA) of the transistor. The fixed potential V_(b)may be the potential V₁ or the potential V₂. In that case, a potentialgenerator circuit for generating the fixed potential V_(b) is notnecessary, which is preferable. The fixed potential V_(b) may bedifferent from the potential V₁ or the potential V₂. When the fixedpotential V_(b) is low, the threshold voltage V_(thA) can be high insome cases. As a result, the drain current flowing when the gate-sourcevoltage V_(gs) is 0 V can be reduced, and leakage current in a circuitincluding the transistor can be reduced in some cases. The fixedpotential V_(b) may be, for example, lower than the low power supplypotential. On the other hand, in some cases, the threshold voltageV_(thA) can be low by setting the fixed potential V_(b) high. As aresult, the drain current generated when the gate-source voltage V_(gs)is a high power supply potential can be increased and the operatingspeed of the circuit including the transistor can be improved in somecases. The fixed potential V_(b) may be, for example, higher than thelow power supply potential.

The signal B is, for example, a signal for controlling the on/off state.The signal B may be a digital signal with two kinds of potentials, apotential V₃ and a potential V₄ (V₃>V₄). For example, the potential V₃can be a high power supply potential, and the potential V₄ can be a lowpower supply potential. The signal B may be an analog signal.

When both the signal A and the signal B are digital signals, the signalB may have the same digital value as the signal A. In this case, it maybe possible to increase the on-state current of the transistor and theoperating speed of the circuit including the transistor. Here, thepotential V₁ and the potential V₂ of the signal A may be different fromthe potential V₃ and the potential V₄ of the signal B. For example, whena gate insulating film for the gate to which the signal B is input isthicker than a gate insulating film for the gate to which the signal Ais input, the potential amplitude of the signal B (V₃-V₄) may be largerthan the potential amplitude of the signal A (V₁-V₂). In this manner,the influence of the signal A and that of the signal B on the on/offstate of the transistor can be substantially the same in some cases.

When both the signal A and the signal B are digital signals, the signalB may have a digital value different from that of the signal A. In thiscase, the signal A and the signal B can separately control thetransistor, and thus, higher performance can be achieved. The transistorwhich is, for example, an n-channel transistor can function by itself asa NAND circuit, a NOR circuit, or the like in the following case: thetransistor is turned on only when the signal A has the potential V₁ andthe signal B has the potential V₃, or the transistor is turned off onlywhen the signal A has the potential V₂ and the signal B has thepotential V₄. The signal B may be a signal for controlling the thresholdvoltage V_(thA). For example, the potential of the signal B in a periodin which the circuit including the transistor operates may be differentfrom the potential of the signal B in a period in which the circuit doesnot operate. The potential of the signal B may vary depending on theoperation mode of the circuit. In this case, the potential of the signalB is not necessarily changed as frequently as the potential of thesignal A.

When both the signal A and the signal B are analog signals, the signal Bmay be an analog signal having the same potential as the signal A, ananalog signal whose potential is a constant times the potential of thesignal A, an analog signal whose potential is higher or lower than thepotential of the signal A by a constant, or the like. In this case, itmay be possible to increase the on-state current of the transistor andthe operating speed of the circuit including the transistor. The signalB may be an analog signal different from the signal A. In this case, thesignal A and the signal B can separately control the transistor, andthus, higher performance can be achieved.

The signal A may be a digital signal, and the signal B may be an analogsignal. Alternatively, the signal A may be an analog signal, and thesignal B may be a digital signal.

When both of the gate electrodes of the transistor are supplied with thefixed potentials, the transistor can function as an element equivalentto a resistor in some cases. For example, in the case where thetransistor is an n-channel transistor, the effective resistance of thetransistor can be sometimes low (high) when the fixed potential V_(a) orthe fixed potential V_(b) is high (low). When both the fixed potentialV_(a) and the fixed potential V_(b) are high (low), the effectiveresistance can be lower (higher) than that of a transistor with only onegate in some cases.

An insulating film may further be formed over the transistor 150. Thetransistor 150 illustrated in FIGS. 22A to 22C includes the insulatingfilm 122 over the conductive films 120 a and 120 b and the insulatingfilm 118.

The insulating film 122 has a function of covering unevenness and thelike caused by the transistor or the like. The insulating film 122 hasan insulating property and is formed using an inorganic material or anorganic material. Examples of the inorganic material include a siliconoxide film, a silicon oxynitride film, a silicon nitride oxide film, asilicon nitride film, an aluminum oxide film, and an aluminum nitridefilm. Examples of the organic material include photosensitive resinmaterials such as an acrylic resin and a polyimide resin.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 8

In this embodiment, structures of a data processor of one embodiment ofthe present invention will be described with reference to FIGS. 19A to19E and FIGS. 20A to 20E.

FIGS. 19A to 19E and FIGS. 20A to 20E illustrate the structures of thedata processor of one embodiment of the present invention. FIG. 19A is ablock diagram of the data processor, and FIGS. 19B to 19E areperspective views illustrating the structures of the data processor.FIGS. 20A to 20E are perspective views illustrating the structures ofthe data processor.

<Data Processor>

A data processor 5200B described in this embodiment includes anarithmetic device 5210 and an input/output device 5220 (see FIG. 19A).

The arithmetic device 5210 has a function of receiving operation dataand a function of supplying image data on the basis of the operationdata.

The input/output device 5220 includes a display portion 5230, an inputportion 5240, a sensor portion 5250, and a communication portion 5290and has a function of supplying operation data and a function ofreceiving image data. The input/output device 5220 also has a functionof supplying sensing data, a function of supplying communication data,and a function of receiving communication data.

The input portion 5240 has a function of supplying operation data. Forexample, the input portion 5240 supplies operation data on the basis ofoperation by a user of the data processor 5200B.

Specifically, a keyboard, a hardware button, a pointing device, a touchsensor, an audio input device, a sight input device, or the like can beused as the input portion 5240.

The display portion 5230 includes a display panel and has a function ofdisplaying image data. For example, the display panel described in anyof other embodiments can be used for the display portion 5230.

The sensor portion 5250 has a function of supplying sensing data. Forexample, the sensor portion 5250 has a function of sensing a surroundingenvironment where the data processor is used and supplying sensing data.

Specifically, an illuminance sensor, an imaging device, a posturedetermination device, a pressure sensor, a human motion sensor, or thelike can be used as the sensor portion 5250.

The communication portion 5290 has a function of receiving and supplyingcommunication data. For example, the communication portion 5290 has afunction of being connected to another electronic device or acommunication network by wireless communication or wired communication.Specifically, the communication portion 5290 has a function of localarea wireless communication, telephone communication, or near fieldwireless communication, for example.

<Structure Example 1 of Data Processor>

The display portion 5230 can have an outer shape along a cylindricalcolumn, for example (see FIG. 19B). The display portion 5230 has afunction of changing a display method in accordance with the illuminanceof a usage environment and a function of changing displayed contentswhen sensing the existence of a person. Thus, the data processor 5200Bcan be mounted on a column of a building, for example. Alternatively,the data processor 5200B can display advertisements, information, or thelike. Furthermore, the data processor 5200B can be used for digitalsignage or the like.

<Structure Example 2 of Data Processor>

The data processor 5200B has a function of generating image data on thebasis of the path of a pointer used by a user, for example (see FIG.19C). Specifically, it is possible to use a display panel with adiagonal of 20 inches or more, preferably 40 inches or more, furtherpreferably 55 inches or more. Alternatively, display panels can bearranged in one display region. Alternatively, display panels can bearranged to be used as a multiscreen. In this case, the data processor5200B can be used for an electronic blackboard, an electronic bulletinboard, digital signage, or the like.

<Structure Example 3 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 19D). Thus, it is possible to obtain a smartwatch with reducedpower consumption, for example. Alternatively, it is possible to obtaina smartwatch that can display an image such that the smartwatch isfavorably used even in an environment with intense external light, e.g.,in the open air under fine weather.

<Structure Example 4 of Data Processor>

The display portion 5230 has a surface gently curved along a sidesurface of a housing, for example (see FIG. 19E). The display portion5230 includes a display panel that has, for example, a function ofperforming display on a front surface, side surfaces, and a top surface.Thus, it is possible to obtain a mobile phone that can display imagedata on not only its front surface but also its side surfaces and topsurface, for example.

<Structure Example 5 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 20A). Thus, it is possible to obtain a smartphone with reducedpower consumption. Alternatively, it is possible to obtain a smartphonethat can display an image such that the smartphone is favorably usedeven in an environment with intense external light, e.g., in the openair under fine weather.

<Structure Example 6 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 20B). Thus, it is possible to obtain a television system that candisplay an image such that the television system is favorably used evenwhen exposed to intense external light poured into a room in a sunnyday.

<Structure Example 7 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 20C). Thus, it is possible to obtain a tablet computer that candisplay an image such that the tablet computer is favorably used even inan environment with intense external light, e.g., in the open air underfine weather.

<Structure Example 8 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 20D). Thus, it is possible to obtain a digital camera that candisplay a subject such that an image is favorably viewed even in anenvironment with intense external light, e.g., in the open air underfine weather.

<Structure Example 9 of Data Processor>

The data processor 5200B has a function of changing a display method inaccordance with the illuminance of a usage environment, for example (seeFIG. 20E). Thus, it is possible to obtain a personal computer that candisplay an image such that the personal computer is favorably used evenin an environment with intense external light, e.g., in the open airunder fine weather.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 9

In this embodiment, a structure of an electronic device of oneembodiment of the present invention will be described with reference toFIG. 23.

<Electronic Device>

FIG. 23 illustrates a foldable electronic device 920. The electronicdevice 920 illustrated in FIG. 23 includes a housing 921 a, a housing921 b, a display portion 922, a hinge 923, and the like. The displayportion 922 is incorporated in the housing 921 a and the housing 921 b.

The housing 921 a and the housing 921 b are rotatably joined to eachother by the hinge 923. The electronic device 920 can be changed inshape between a state where the housing 921 a and the housing 921 b areclosed and a state where the housing 921 a and the housing 921 b areopened as illustrated in FIG. 23. Thus, the electronic device 920 hashigh portability when carried and excellent visibility when used becauseof its large display region.

The hinge 923 preferably includes a locking mechanism so that an angleformed between the housing 921 a and the housing 921 b does not becomelarger than a predetermined angle when the housing 921 a and the housing921 b are opened. For example, an angle at which the housing 921 a andthe housing 921 b become locked (they are not opened any further) ispreferably greater than or equal to 90° and less than 180° and istypically 90°, 120°, 135°, 150°, 175°, or the like. In that case, theconvenience, the safety, and the reliability can be improved.

In the electronic device 920, the flexible display portion 922 isprovided across the housing 921 a and the housing 921 b which are joinedto each other by the hinge 923.

In the electronic device 920, the display portion 922 is greatly curvedwith the housing 921 a and the housing 921 b open. For example, thedisplay portion 922 is held with a curvature radius of 1 mm or greaterand 50 mm or less, preferably 5 mm or greater and 30 mm or less. Part ofthe display portion 922 can display an image while being bent sincepixels are continuously arranged from the housing 921 a to the housing921 b.

Since the hinge 923 includes the above-described locking mechanism,excessive force is not applied to the display portion 922; thus,breakage of the display portion 922 can be prevented. Consequently, ahighly reliable electronic device can be obtained.

The display portion 922 functions as a touch panel and can be controlledwith a finger, a stylus, or the like.

One of the housing 921 a and the housing 921 b is provided with awireless communication module, and data can be transmitted and receivedthrough a computer network such as the Internet, a local area network(LAN), or Wi-Fi (registered trademark).

The display portion 922 is preferably formed using one flexible display.Thus, a continuous image can be displayed between the housing 921 a andthe housing 921 b. Note that each of the housing 921 a and the housing921 b may be provided with a display.

At least part of this embodiment can be implemented in combination withany of the other embodiments described in this specification asappropriate.

For example, in this specification and the like, an explicit description“X and Y are connected” means that X and Y are electrically connected, Xand Y are functionally connected, and X and Y are directly connected.Accordingly, without being limited to a predetermined connectionrelationship, for example, a connection relationship shown in drawingsor texts, another connection relationship is included in the drawings orthe texts.

Here, X and Y each denote an object (e.g., a device, an element, acircuit, a wiring, an electrode, a terminal, a conductive film, or alayer).

Examples of the case where X and Y are directly connected include thecase where an element that allows an electrical connection between X andY (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) is notconnected between X and Y, and the case where X and Y are connectedwithout the element that allows the electrical connection between X andY provided therebetween.

For example, in the case where X and Y are electrically connected, oneor more elements that enable an electrical connection between X and Y(e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) can beconnected between X and Y. Note that the switch is controlled to beturned on or off. That is, the switch is conducting or not conducting(is turned on or off) to determine whether current flows therethrough ornot. Alternatively, the switch has a function of selecting and changinga current path. Note that the case where X and Y are electricallyconnected includes the case where X and Y are directly connected.

For example, in the case where X and Y are functionally connected, oneor more circuits that enable a functional connection between X and Y(e.g., a logic circuit such as an inverter, a NAND circuit, or a NORcircuit; a signal converter circuit such as a D/A converter circuit, anA/D converter circuit, or a gamma correction circuit; a potential levelconverter circuit such as a power supply circuit (e.g., a step-upcircuit or a step-down circuit) or a level shifter circuit for changingthe potential level of a signal; a voltage source; a current source; aswitching circuit; an amplifier circuit such as a circuit that canincrease signal amplitude, the amount of current, or the like, anoperational amplifier, a differential amplifier circuit, a sourcefollower circuit, and a buffer circuit; a signal generation circuit; amemory circuit; or a control circuit) can be connected between X and Y.For example, even when another circuit is interposed between X and Y, Xand Y are functionally connected when a signal output from X istransmitted to Y. Note that the case where X and Y are functionallyconnected includes the case where X and Y are directly connected and thecase where X and Y are electrically connected.

Note that in this specification and the like, an explicit description “Xand Y are electrically connected” means that X and Y are electricallyconnected (i.e., the case where X and Y are connected with anotherelement or another circuit provided therebetween), X and Y arefunctionally connected (i.e., the case where X and Y are functionallyconnected with another circuit provided therebetween), and X and Y aredirectly connected (i.e., the case where X and Y are connected withoutanother element or another circuit provided therebetween). That is, inthis specification and the like, the explicit description “X and Y areelectrically connected” is the same as the description “X and Y areconnected”.

For example, any of the following expressions can be used for the casewhere a source (or a first terminal or the like) of a transistor iselectrically connected to X through (or not through) Z1 and a drain (ora second terminal or the like) of the transistor is electricallyconnected to Y through (or not through) Z2, or the case where a source(or a first terminal or the like) of a transistor is directly connectedto one part of Z1 and another part of Z1 is directly connected to Xwhile a drain (or a second terminal or the like) of the transistor isdirectly connected to one part of Z2 and another part of Z2 is directlyconnected to Y.

Examples of the expressions include, “X, Y, a source (or a firstterminal or the like) of a transistor, and a drain (or a second terminalor the like) of the transistor are electrically connected to each other,and X, the source (or the first terminal or the like) of the transistor,the drain (or the second terminal or the like) of the transistor, and Yare electrically connected to each other in this order”, “a source (or afirst terminal or the like) of a transistor is electrically connected toX, a drain (or a second terminal or the like) of the transistor iselectrically connected to Y, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are electrically connected to each otherin this order”, and “X is electrically connected to Y through a source(or a first terminal or the like) and a drain (or a second terminal orthe like) of a transistor, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are provided to be connected in thisorder”. When the connection order in a circuit configuration is definedby an expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope.

Other examples of the expressions include, “a source (or a firstterminal or the like) of a transistor is electrically connected to Xthrough at least a first connection path, the first connection path doesnot include a second connection path, the second connection path is apath between the source (or the first terminal or the like) of thetransistor and a drain (or a second terminal or the like) of thetransistor, Z1 is on the first connection path, the drain (or the secondterminal or the like) of the transistor is electrically connected to Ythrough at least a third connection path, the third connection path doesnot include the second connection path, and Z2 is on the thirdconnection path” and “a source (or a first terminal or the like) of atransistor is electrically connected to X at least with a firstconnection path through Z1, the first connection path does not include asecond connection path, the second connection path includes a connectionpath through which the transistor is provided, a drain (or a secondterminal or the like) of the transistor is electrically connected to Yat least with a third connection path through Z2, and the thirdconnection path does not include the second connection path”. Stillanother example of the expression is “a source (or a first terminal orthe like) of a transistor is electrically connected to X through atleast Z1 on a first electrical path, the first electrical path does notinclude a second electrical path, the second electrical path is anelectrical path from the source (or the first terminal or the like) ofthe transistor to a drain (or a second terminal or the like) of thetransistor, the drain (or the second terminal or the like) of thetransistor is electrically connected to Y through at least Z2 on a thirdelectrical path, the third electrical path does not include a fourthelectrical path, and the fourth electrical path is an electrical pathfrom the drain (or the second terminal or the like) of the transistor tothe source (or the first terminal or the like) of the transistor”. Whenthe connection path in a circuit configuration is defined by anexpression similar to the above examples, a source (or a first terminalor the like) and a drain (or a second terminal or the like) of atransistor can be distinguished from each other to specify the technicalscope.

Note that these expressions are examples and there is no limitation onthe expressions. Here, X, Y, Z1, and Z2 each denote an object (e.g., adevice, an element, a circuit, a wiring, an electrode, a terminal, aconductive film, and a layer).

Even when independent components are electrically connected to eachother in a circuit diagram, one component has functions of a pluralityof components in some cases. For example, when part of a wiring alsofunctions as an electrode, one conductive film functions as the wiringand the electrode. Thus, “electrical connection” in this specificationincludes in its category such a case where one conductive film hasfunctions of a plurality of components.

This application is based on Japanese Patent Application Serial No.2016-202528 filed with Japan Patent Office on Oct. 14, 2016, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. An input/output panel comprising: a gate wiring;a first wiring electrode; a second wiring electrode; a current sensingcircuit; and a pixel, wherein the first wiring electrode is parallel toand directly electrically connected to the gate wiring via a thirdwiring electrode in a contact region, wherein the second wiringelectrode intersects with the gate wiring, wherein the first wiringelectrode and the second wiring electrode intersect and a capacitance isgenerated at the intersection, wherein the current sensing circuit iselectrically connected to the second wiring electrode, wherein thecurrent sensing circuit is configured to sense a change in thecapacitance for determining a touch, wherein the pixel comprises atransistor and a display element, wherein the transistor comprises agate electrode, a source electrode, and a drain electrode, wherein thegate electrode is electrically connected to the gate wiring, wherein thedisplay element comprises a third electrode and a liquid crystalmaterial, and wherein the third electrode is electrically connected tothe source electrode or the drain electrode.
 2. The input/output panelaccording to claim 1, wherein an electric field controlling alignment ofthe liquid crystal material is generated between the second wiringelectrode and the third electrode, and wherein the third electrode isbetween the liquid crystal material and the second wiring electrode. 3.The input/output panel according to claim 1, wherein the display elementcomprises a fourth electrode, wherein an electric field controllingalignment of the liquid crystal material is generated between the thirdelectrode and the fourth electrode, wherein the fourth electrode iselectrically connected to a wiring supplied with a common potential, andwherein the third electrode is between the liquid crystal material andthe fourth electrode.
 4. The input/output panel according to claim 3,wherein the first wiring electrode comprises the same material as thethird electrode, and wherein the second wiring electrode comprises thesame material as the fourth electrode.
 5. The input/output panelaccording to claim 2, further comprising: a backlight, wherein one orboth of the second wiring electrode and the third electrode havereflectance greater than or equal to 5% and less than 100% and lighttransmittance greater than or equal to 1% and less than 95% with respectto light with a wavelength in a range greater than or equal to 400 nmand less than 800 nm, and wherein the backlight is configured to emitlight through a layer comprising the liquid crystal material.
 6. Theinput/output panel according to claim 3, further comprising: abacklight, wherein one or both of the third electrode and the fourthelectrode have reflectance greater than or equal to 5% and less than100% and light transmittance greater than or equal to 1% and less than95% with respect to light with a wavelength in a range greater than orequal to 400 nm and less than 800 nm, and wherein the backlight isconfigured to emit light through a layer comprising the liquid crystalmaterial.
 7. A semiconductor device comprising: one or more of akeyboard, a hardware button, a pointing device, a touch sensor, anilluminance sensor, an imaging device, an audio input device, a sightinput device, and a posture determination device; and the input/outputpanel according to claim
 1. 8. An input/output panel comprising: a gatewiring; a first wiring electrode; a second wiring electrode; a currentsensing circuit; and a pixel, wherein the first wiring electrode isparallel to and directly electrically connected to the gate wiring via athird wiring electrode in a contact region, wherein the second wiringelectrode intersects with the gate wiring, wherein the first wiringelectrode and the second wiring electrode intersect and a capacitance isgenerated at the intersection, wherein the current sensing circuit iselectrically connected to the second wiring electrode, wherein thecurrent sensing circuit is configured to sense a change in thecapacitance for determining a touch, wherein the pixel comprises a firsttransistor, a second transistor, and a light-emitting element, whereinthe first transistor comprises a first gate electrode, a first sourceelectrode, and a first drain electrode, wherein the second transistorcomprises a second gate electrode, a second source electrode, and asecond drain electrode, wherein the first gate electrode is electricallyconnected to the gate wiring, wherein the first source electrode or thefirst drain electrode is electrically connected to the second gateelectrode, and wherein the second source electrode or the second drainelectrode supplies electric power for driving the light-emittingelement.
 9. A semiconductor device comprising: one or more of akeyboard, a hardware button, a pointing device, a touch sensor, anilluminance sensor, an imaging device, an audio input device, a sightinput device, and a posture determination device; and the input/outputpanel according to claim 8.